The determination of periods of access between a satellite constellation and targets on the surface of the Earth is a computationally expensive, extremely time-consuming process. A typical example would involve calculating access between 3,000 or more sensors (e.g., a constellation of 66 satellites, each having 48 sensors) and 3,000 or more targets, including many area targets of irregular shape--a total of more than 9 million access calculations. Even with high speed computer equipment employing state-of-the art satellite system analysis software, calculating a week of access under such circumstances would require nearly a year of processing time. A more limited problem--such as calculating loss of access due to failure of one or more sensors on a given satellite in the constellation--could take several hours to process.
To overcome the shortcomings of approaches used to date, a method and apparatus is needed that will yield quick and accurate estimates of access times, based on a series of access calculations performed in advance for a single (possibly hypothetical) satellite over a systematically selected set of revolutions. Using the pre-computed access calculations as a baseline, such a method would estimate the access times between a given satellite in the constellation and a given target by interpolation and other appropriate adjustments. As the calculations required for interpolation and correction factors are much simpler than those required to actually calculate access between satellite constellations and ground targets, such a method would provide this necessary information in a much more timely manner.